package touchinput;

/**
 * MultiTouchController.java
 *
 * Author: Luke Hutchison (luke.hutch@mit.edu)
 *   Please drop me an email if you use this code so I can list your project here!
 *
 * Usage:
 *   <code>
 *   public class MyMTView extends View implements MultiTouchObjectCanvas<PinchWidgetType> {
 *
 *       private MultiTouchController<PinchWidgetType> multiTouchController = new MultiTouchController<PinchWidgetType>(this);
 *
 *       // Pass touch events to the MT controller
 *       public boolean onTouchEvent(MotionEvent event) {
 *           return multiTouchController.onTouchEvent(event);
 *       }
 *
 *       // ... then implement the MultiTouchObjectCanvas interface here, see details in the comments of that interface.
 *   }
 *   </code>
 *
 * Changelog:
 *   2010-06-09 v1.5.1  Some API changes to make it possible to selectively update or not update scale / rotation.
 *                      Fixed anisotropic zoom.  Cleaned up rotation code.  Added more comments.  Better var names. (LH)
 *   2010-06-09 v1.4    Added ability to track pinch rotation (Mickael Despesse, author of "Face Frenzy") and anisotropic pinch-zoom (LH)
 *   2010-06-09 v1.3.3  Bugfixes for Android-2.1; added optional debug info (LH)
 *   2010-06-09 v1.3    Ported to Android-2.2 (handle ACTION_POINTER_* actions); fixed several bugs; refactoring; documentation (LH)
 *   2010-05-17 v1.2.1  Dual-licensed under Apache and GPL licenses
 *   2010-02-18 v1.2    Support for compilation under Android 1.5/1.6 using introspection (mmin, author of handyCalc)
 *   2010-01-08 v1.1.1  Bugfixes to Cyanogen's patch that only showed up in more complex uses of controller (LH)
 *   2010-01-06 v1.1    Modified for official level 5 MT API (Cyanogen)
 *   2009-01-25 v1.0    Original MT controller, released for hacked G1 kernel (LH)
 *
 * Planned features:
 * - Add inertia (flick-pinch-zoom or flick-scroll)
 *
 * Known usages:
 * - Mickael Despesse's "Face Frenzy" face distortion app, to be published to the Market soon
 * - Yuan Chin's fork of ADW Launcher to support multitouch
 * - David Byrne's fractal viewing app Fractoid
 * - mmin's handyCalc calculator
 * - My own "MultiTouch Visualizer 2" in the Market
 * - Formerly: The browser in cyanogenmod (and before that, JesusFreke), and other firmwares like dwang5.  This usage has been
 *   replaced with official pinch/zoom in Maps, Browser and Gallery[3D] as of API level 5.
 *
 * License:
 *   Dual-licensed under the Apache License v2 and the GPL v2.
 */

import android.util.Log;
import android.view.MotionEvent;

import java.lang.reflect.Method;

/**
 * A class that simplifies the implementation of multitouch in applications. Subclass this and read the fields here as needed in subclasses.
 *
 * @author Luke Hutchison
 */
public class MultiTouchController<T> {

  /**
   * Time in ms required after a change in event status (e.g. putting down or lifting off the second finger) before events actually do anything --
   * helps eliminate noisy jumps that happen on change of status
   */
  private static final long EVENT_SETTLE_TIME_INTERVAL = 20;
  /**
   * The biggest possible abs val of the change in x or y between multitouch events (larger dx/dy events are ignored) -- helps eliminate jumps in
   * pointer position on finger 2 up/down.
   */
  private static final float MAX_MULTITOUCH_POS_JUMP_SIZE = 30.0f;
  /**
   * The biggest possible abs val of the change in multitouchWidth or multitouchHeight between multitouch events (larger-jump events are ignored) --
   * helps eliminate jumps in pointer position on finger 2 up/down.
   */
  private static final float MAX_MULTITOUCH_DIM_JUMP_SIZE = 40.0f;
  /**
   * The smallest possible distance between multitouch points (used to avoid div-by-zero errors and display glitches)
   */
  private static final float MIN_MULTITOUCH_SEPARATION = 30.0f;
  /**
   * The max number of touch points that can be present on the screen at once
   */
  public static final int MAX_TOUCH_POINTS = 20;
  /**
   * Generate tons of log entries for debugging
   */
  public static final boolean DEBUG = false;
  // ----------------------------------------------------------------------------------------------------------------------
  MultiTouchObjectCanvas<T> objectCanvas;
  /**
   * The current touch point
   */
  private PointInfo mCurrPt;
  /**
   * The previous touch point
   */
  private PointInfo mPrevPt;
  /**
   * Fields extracted from mCurrPt
   */
  private float mCurrPtX, mCurrPtY, mCurrPtDiam, mCurrPtWidth, mCurrPtHeight, mCurrPtAng;

  /**
   * Extract fields from mCurrPt, respecting the update* fields of mCurrPt. This just avoids code duplication. I hate that Java doesn't support
   * higher-order functions, tuples or multiple return values from functions.
   */
  private void extractCurrPtInfo() {
    // Get new drag/pinch params. Only read multitouch fields that are needed,
    // to avoid unnecessary computation (diameter and angle are expensive operations).
    mCurrPtX = mCurrPt.getX();
    mCurrPtY = mCurrPt.getY();
    mCurrPtDiam = Math.max(MIN_MULTITOUCH_SEPARATION * .71f, !mCurrXform.updateScale ? 0.0f : mCurrPt.getMultiTouchDiameter());
    mCurrPtWidth = Math.max(MIN_MULTITOUCH_SEPARATION, !mCurrXform.updateScaleXY ? 0.0f : mCurrPt.getMultiTouchWidth());
    mCurrPtHeight = Math.max(MIN_MULTITOUCH_SEPARATION, !mCurrXform.updateScaleXY ? 0.0f : mCurrPt.getMultiTouchHeight());
    mCurrPtAng = !mCurrXform.updateAngle ? 0.0f : mCurrPt.getMultiTouchAngle();
  }
  // ----------------------------------------------------------------------------------------------------------------------
  /**
   * Whether to handle single-touch events/drags before multi-touch is initiated or not; if not, they are handled by subclasses
   */
  private boolean handleSingleTouchEvents;
  /**
   * The object being dragged/stretched
   */
  private T selectedObject = null;
  /**
   * Current position and scale of the dragged object
   */
  private PositionAndScale mCurrXform = new PositionAndScale();
  /**
   * Drag/pinch start time and time to ignore spurious events until (to smooth over event noise)
   */
  private long mSettleStartTime, mSettleEndTime;
  /**
   * Conversion from object coords to screen coords
   */
  private float startPosX, startPosY;
  /**
   * Conversion between scale and width, and object angle and start pinch angle
   */
  private float startScaleOverPinchDiam, startAngleMinusPinchAngle;
  /**
   * Conversion between X scale and width, and Y scale and height
   */
  private float startScaleXOverPinchWidth, startScaleYOverPinchHeight;
  // ----------------------------------------------------------------------------------------------------------------------
  /**
   * No touch points down.
   */
  private static final int MODE_NOTHING = 0;
  /**
   * One touch point down, dragging an object.
   */
  private static final int MODE_DRAG = 1;
  /**
   * Two or more touch points down, stretching/rotating an object using the first two touch points.
   */
  private static final int MODE_PINCH = 2;
  /**
   * Current drag mode
   */
  private int mMode = MODE_NOTHING;

  // ----------------------------------------------------------------------------------------------------------------------

  /**
   * Constructor that sets handleSingleTouchEvents to true
   */
  public MultiTouchController(MultiTouchObjectCanvas<T> objectCanvas) {
    this(objectCanvas, true);
  }

  /**
   * Full constructor
   */
  public MultiTouchController(MultiTouchObjectCanvas<T> objectCanvas, boolean handleSingleTouchEvents) {
    this.mCurrPt = new PointInfo();
    this.mPrevPt = new PointInfo();
    this.handleSingleTouchEvents = handleSingleTouchEvents;
    this.objectCanvas = objectCanvas;
  }

  // ------------------------------------------------------------------------------------

  /**
   * Whether to handle single-touch events/drags before multi-touch is initiated or not; if not, they are handled by subclasses. Default: true
   */
  protected void setHandleSingleTouchEvents(boolean handleSingleTouchEvents) {
    this.handleSingleTouchEvents = handleSingleTouchEvents;
  }

  /**
   * Whether to handle single-touch events/drags before multi-touch is initiated or not; if not, they are handled by subclasses. Default: true
   */
  protected boolean getHandleSingleTouchEvents() {
    return handleSingleTouchEvents;
  }

  // ------------------------------------------------------------------------------------
  public static final boolean multiTouchSupported;
  private static Method m_getPointerCount;
  private static Method m_getPointerId;
  private static Method m_getPressure;
  private static Method m_getHistoricalX;
  private static Method m_getHistoricalY;
  private static Method m_getHistoricalPressure;
  private static Method m_getX;
  private static Method m_getY;
  private static int ACTION_POINTER_UP = 6;
  private static int ACTION_POINTER_INDEX_SHIFT = 8;

  static {
    boolean succeeded = false;
    try {
      // Android 2.0.1 stuff:
      m_getPointerCount = MotionEvent.class.getMethod("getPointerCount");
      m_getPointerId = MotionEvent.class.getMethod("getPointerId", Integer.TYPE);
      m_getPressure = MotionEvent.class.getMethod("getPressure", Integer.TYPE);
      m_getHistoricalX = MotionEvent.class.getMethod("getHistoricalX", Integer.TYPE, Integer.TYPE);
      m_getHistoricalY = MotionEvent.class.getMethod("getHistoricalY", Integer.TYPE, Integer.TYPE);
      m_getHistoricalPressure = MotionEvent.class.getMethod("getHistoricalPressure", Integer.TYPE, Integer.TYPE);
      m_getX = MotionEvent.class.getMethod("getX", Integer.TYPE);
      m_getY = MotionEvent.class.getMethod("getY", Integer.TYPE);
      succeeded = true;
    } catch (Exception e) {
      Log.e("MultiTouchController", "static initializer failed", e);
    }
    multiTouchSupported = succeeded;
    if (multiTouchSupported) {
      // Android 2.2+ stuff (the original Android 2.2 consts are declared above,
      // and these actions aren't used previous to Android 2.2):
      try {
        ACTION_POINTER_UP = MotionEvent.class.getField("ACTION_POINTER_UP").getInt(null);
        ACTION_POINTER_INDEX_SHIFT = MotionEvent.class.getField("ACTION_POINTER_INDEX_SHIFT").getInt(null);
      } catch (Exception e) {
      }
    }
  }

  // ------------------------------------------------------------------------------------
  private static final float[] xVals = new float[MAX_TOUCH_POINTS];
  private static final float[] yVals = new float[MAX_TOUCH_POINTS];
  private static final float[] pressureVals = new float[MAX_TOUCH_POINTS];
  private static final int[] pointerIds = new int[MAX_TOUCH_POINTS];

  /**
   * Process incoming touch events
   */
  public boolean onTouchEvent(MotionEvent event) {
    try {
      int pointerCount = multiTouchSupported ? (Integer) m_getPointerCount.invoke(event) : 1;
      if (DEBUG) {
        Log.i("MultiTouch", "Got here 1 - " + multiTouchSupported + " " + mMode + " " + handleSingleTouchEvents + " " + pointerCount);
      }
      if (mMode == MODE_NOTHING && !handleSingleTouchEvents && pointerCount == 1) // Not handling initial single touch events, just pass them on
      {
        return false;
      }
      if (DEBUG) {
        Log.i("MultiTouch", "Got here 2");
      }

      // Handle history first (we sometimes get history with ACTION_MOVE events)
      int action = event.getAction();
      int histLen = event.getHistorySize() / pointerCount;
      for (int histIdx = 0; histIdx <= histLen; histIdx++) {
        // Read from history entries until histIdx == histLen, then read from current event
        boolean processingHist = histIdx < histLen;
        if (!multiTouchSupported || pointerCount == 1) {
          // Use single-pointer methods -- these are needed as a special case (for some weird reason) even if
          // multitouch is supported but there's only one touch point down currently -- event.getX(0) etc. throw
          // an exception if there's only one point down.
          if (DEBUG) {
            Log.i("MultiTouch", "Got here 3");
          }
          xVals[0] = processingHist ? event.getHistoricalX(histIdx) : event.getX();
          yVals[0] = processingHist ? event.getHistoricalY(histIdx) : event.getY();
          pressureVals[0] = processingHist ? event.getHistoricalPressure(histIdx) : event.getPressure();
        } else {
          // Read x, y and pressure of each pointer
          if (DEBUG) {
            Log.i("MultiTouch", "Got here 4");
          }
          int numPointers = Math.min(pointerCount, MAX_TOUCH_POINTS);
          if (DEBUG && pointerCount > MAX_TOUCH_POINTS) {
            Log.i("MultiTouch", "Got more pointers than MAX_TOUCH_POINTS");
          }
          for (int ptrIdx = 0; ptrIdx < numPointers; ptrIdx++) {
            int ptrId = (Integer) m_getPointerId.invoke(event, ptrIdx);
            pointerIds[ptrIdx] = ptrId;
            // N.B. if pointerCount == 1, then the following methods throw an array index out of range exception,
            // and the code above is therefore required not just for Android 1.5/1.6 but also for when there is
            // only one touch point on the screen -- pointlessly inconsistent :(
            xVals[ptrIdx] = (Float) (processingHist ? m_getHistoricalX.invoke(event, ptrIdx, histIdx) : m_getX.invoke(event, ptrIdx));
            yVals[ptrIdx] = (Float) (processingHist ? m_getHistoricalY.invoke(event, ptrIdx, histIdx) : m_getY.invoke(event, ptrIdx));
            pressureVals[ptrIdx] = (Float) (processingHist ? m_getHistoricalPressure.invoke(event, ptrIdx, histIdx) : m_getPressure.invoke(event, ptrIdx));
          }
        }
        // Decode event
        decodeTouchEvent(pointerCount, xVals, yVals, pressureVals, pointerIds, //
            /* action = */ processingHist ? MotionEvent.ACTION_MOVE : action, //
            /* down = */ processingHist ? true : action != MotionEvent.ACTION_UP //
            && (action & ((1 << ACTION_POINTER_INDEX_SHIFT) - 1)) != ACTION_POINTER_UP //
            && action != MotionEvent.ACTION_CANCEL, //
            processingHist ? event.getHistoricalEventTime(histIdx) : event.getEventTime());
      }

      return true;
    } catch (Exception e) {
      // In case any of the introspection stuff fails (it shouldn't)
      Log.e("MultiTouchController", "onTouchEvent() failed", e);
      return false;
    }
  }

  private void decodeTouchEvent(int pointerCount, float[] x, float[] y, float[] pressure, int[] pointerIds, int action, boolean down, long eventTime) {
    if (DEBUG) {
      Log.i("MultiTouch", "Got here 5 - " + pointerCount + " " + action + " " + down);
    }

    // Swap curr/prev points
    PointInfo tmp = mPrevPt;
    mPrevPt = mCurrPt;
    mCurrPt = tmp;
    // Overwrite old prev point
    mCurrPt.set(pointerCount, x, y, pressure, pointerIds, action, down, eventTime);
    multiTouchController();
  }

  // ------------------------------------------------------------------------------------

  /**
   * Start dragging/pinching, or reset drag/pinch to current point if something goes out of range
   */
  private void anchorAtThisPositionAndScale() {
    if (selectedObject == null) {
      return;
    }

    // Get selected object's current position and scale
    objectCanvas.getPositionAndScale(selectedObject, mCurrXform);

    // Figure out the object coords of the drag start point's screen coords.
    // All stretching should be around this point in object-coord-space.
    // Also figure out out ratio between object scale factor and multitouch
    // diameter at beginning of drag; same for angle and optional anisotropic
    // scale.
    float currScaleInv = 1.0f / (!mCurrXform.updateScale ? 1.0f : mCurrXform.scale == 0.0f ? 1.0f : mCurrXform.scale);
    extractCurrPtInfo();
    startPosX = (mCurrPtX - mCurrXform.xOff) * currScaleInv;
    startPosY = (mCurrPtY - mCurrXform.yOff) * currScaleInv;
    startScaleOverPinchDiam = mCurrXform.scale / mCurrPtDiam;
    startScaleXOverPinchWidth = mCurrXform.scaleX / mCurrPtWidth;
    startScaleYOverPinchHeight = mCurrXform.scaleY / mCurrPtHeight;
    startAngleMinusPinchAngle = mCurrXform.angle - mCurrPtAng;
  }

  /**
   * Drag/stretch/rotate the selected object using the current touch position(s) relative to the anchor position(s).
   */
  private void performDragOrPinch() {
    // Don't do anything if we're not dragging anything
    if (selectedObject == null) {
      return;
    }

    // Calc new position of dragged object
    float currScale = !mCurrXform.updateScale ? 1.0f : mCurrXform.scale == 0.0f ? 1.0f : mCurrXform.scale;
    extractCurrPtInfo();
    float newPosX = mCurrPtX - startPosX * currScale;
    float newPosY = mCurrPtY - startPosY * currScale;
    float newScale = startScaleOverPinchDiam * mCurrPtDiam;
    float newScaleX = startScaleXOverPinchWidth * mCurrPtWidth;
    float newScaleY = startScaleYOverPinchHeight * mCurrPtHeight;
    float newAngle = startAngleMinusPinchAngle + mCurrPtAng;

    // Set the new obj coords, scale, and angle as appropriate (notifying the subclass of the change).
    mCurrXform.set(newPosX, newPosY, newScale, newScaleX, newScaleY, newAngle);

    boolean success = objectCanvas.setPositionAndScale(selectedObject, mCurrXform, mCurrPt);
    if (!success)
      ; // If we could't set those params, do nothing currently
  }

  /**
   * State-based controller for tracking switches between no-touch, single-touch and multi-touch situations. Includes logic for cleaning up the
   * event stream, as events around touch up/down are noisy at least on early Synaptics sensors.
   */
  private void multiTouchController() {
    if (DEBUG) {
      Log.i("MultiTouch", "Got here 6 - " + mMode + " " + mCurrPt.getNumTouchPoints() + " " + mCurrPt.isDown() + mCurrPt.isMultiTouch());
    }

    switch (mMode) {
      case MODE_NOTHING:
        // Not doing anything currently
        if (mCurrPt.isDown()) {
          // Start a new single-point drag
          selectedObject = objectCanvas.getDraggableObjectAtPoint(mCurrPt);
          if (selectedObject != null) {
            // Started a new single-point drag
            mMode = MODE_DRAG;
            objectCanvas.selectObject(selectedObject, mCurrPt);
            anchorAtThisPositionAndScale();
            // Don't need any settling time if just placing one finger, there is no noise
            mSettleStartTime = mSettleEndTime = mCurrPt.getEventTime();
          }
        }
        break;

      case MODE_DRAG:
        // Currently in a single-point drag
        if (!mCurrPt.isDown()) {
          // First finger was released, stop dragging
          mMode = MODE_NOTHING;
          objectCanvas.selectObject((selectedObject = null), mCurrPt);

        } else if (mCurrPt.isMultiTouch()) {
          // Point 1 was already down and point 2 was just placed down
          mMode = MODE_PINCH;
          // Restart the drag with the new drag position (that is at the midpoint between the touchpoints)
          anchorAtThisPositionAndScale();
          // Need to let events settle before moving things, to help with event noise on touchdown
          mSettleStartTime = mCurrPt.getEventTime();
          mSettleEndTime = mSettleStartTime + EVENT_SETTLE_TIME_INTERVAL;

        } else {
          // Point 1 is still down and point 2 did not change state, just do single-point drag to new location
          if (mCurrPt.getEventTime() < mSettleEndTime) {
            // Ignore the first few events if we just stopped stretching, because if finger 2 was kept down while
            // finger 1 is lifted, then point 1 gets mapped to finger 2. Restart the drag from the new position.
            anchorAtThisPositionAndScale();
          } else {
            // Keep dragging, move to new point
            performDragOrPinch();
          }
        }
        break;

      case MODE_PINCH:
        // Two-point pinch-scale/rotate/translate
        if (!mCurrPt.isMultiTouch() || !mCurrPt.isDown()) {
          // Dropped one or both points, stop stretching

          if (!mCurrPt.isDown()) {
            // Dropped both points, go back to doing nothing
            mMode = MODE_NOTHING;
            objectCanvas.selectObject((selectedObject = null), mCurrPt);

          } else {
            // Just dropped point 2, downgrade to a single-point drag
            mMode = MODE_DRAG;
            // Restart the pinch with the single-finger position
            anchorAtThisPositionAndScale();
            // Ignore the first few events after the drop, in case we dropped finger 1 and left finger 2 down
            mSettleStartTime = mCurrPt.getEventTime();
            mSettleEndTime = mSettleStartTime + EVENT_SETTLE_TIME_INTERVAL;
          }

        } else {
          // Still pinching
          if (Math.abs(mCurrPt.getX() - mPrevPt.getX()) > MAX_MULTITOUCH_POS_JUMP_SIZE
              || Math.abs(mCurrPt.getY() - mPrevPt.getY()) > MAX_MULTITOUCH_POS_JUMP_SIZE
              || Math.abs(mCurrPt.getMultiTouchWidth() - mPrevPt.getMultiTouchWidth()) * .5f > MAX_MULTITOUCH_DIM_JUMP_SIZE
              || Math.abs(mCurrPt.getMultiTouchHeight() - mPrevPt.getMultiTouchHeight()) * .5f > MAX_MULTITOUCH_DIM_JUMP_SIZE) {
            // Jumped too far, probably event noise, reset and ignore events for a bit
            anchorAtThisPositionAndScale();
            mSettleStartTime = mCurrPt.getEventTime();
            mSettleEndTime = mSettleStartTime + EVENT_SETTLE_TIME_INTERVAL;

          } else if (mCurrPt.eventTime < mSettleEndTime) {
            // Events have not yet settled, reset
            anchorAtThisPositionAndScale();
          } else {
            // Stretch to new position and size
            performDragOrPinch();
          }
        }
        break;
    }
    if (DEBUG) {
      Log.i("MultiTouch", "Got here 7 - " + mMode + " " + mCurrPt.getNumTouchPoints() + " " + mCurrPt.isDown() + mCurrPt.isMultiTouch());
    }
  }

  // ------------------------------------------------------------------------------------

  /**
   * A class that packages up all MotionEvent information with all derived multitouch information (if available)
   */
  public static class PointInfo {
    // Multitouch information

    private int numPoints;
    private float[] xs = new float[MAX_TOUCH_POINTS];
    private float[] ys = new float[MAX_TOUCH_POINTS];
    private float[] pressures = new float[MAX_TOUCH_POINTS];
    private int[] pointerIds = new int[MAX_TOUCH_POINTS];
    // Midpoint of pinch operations
    private float xMid, yMid, pressureMid;
    // Width/diameter/angle of pinch operations
    private float dx, dy, diameter, diameterSq, angle;
    // Whether or not there is at least one finger down (isDown) and/or at least two fingers down (isMultiTouch)
    private boolean isDown, isMultiTouch;
    // Whether or not these fields have already been calculated, for caching purposes
    private boolean diameterSqIsCalculated, diameterIsCalculated, angleIsCalculated;
    // Event action code and event time
    private int action;
    private long eventTime;

    // -------------------------------------------------------------------------------------------------------------------------------------------

    /**
     * Set all point info
     */
    private void set(int numPoints, float[] x, float[] y, float[] pressure, int[] pointerIds, int action, boolean isDown, long eventTime) {
      if (DEBUG) {
        Log.i("MultiTouch", "Got here 8 - " + +numPoints + " " + x[0] + " " + y[0] + " " + (numPoints > 1 ? x[1] : x[0]) + " "
            + (numPoints > 1 ? y[1] : y[0]) + " " + action + " " + isDown);
      }
      this.eventTime = eventTime;
      this.action = action;
      this.numPoints = numPoints;
      for (int i = 0; i < numPoints; i++) {
        this.xs[i] = x[i];
        this.ys[i] = y[i];
        this.pressures[i] = pressure[i];
        this.pointerIds[i] = pointerIds[i];
      }
      this.isDown = isDown;
      this.isMultiTouch = numPoints >= 2;

      if (isMultiTouch) {
        xMid = (x[0] + x[1]) * .5f;
        yMid = (y[0] + y[1]) * .5f;
        pressureMid = (pressure[0] + pressure[1]) * .5f;
        dx = Math.abs(x[1] - x[0]);
        dy = Math.abs(y[1] - y[0]);

      } else {
        // Single-touch event
        xMid = x[0];
        yMid = y[0];
        pressureMid = pressure[0];
        dx = dy = 0.0f;
      }
      // Need to re-calculate the expensive params if they're needed
      diameterSqIsCalculated = diameterIsCalculated = angleIsCalculated = false;
    }

    /**
     * Copy all fields from one PointInfo class to another. PointInfo objects are volatile so you should use this if you want to keep track of the
     * last touch event in your own code.
     */
    public void set(PointInfo other) {
      this.numPoints = other.numPoints;
      for (int i = 0; i < numPoints; i++) {
        this.xs[i] = other.xs[i];
        this.ys[i] = other.ys[i];
        this.pressures[i] = other.pressures[i];
        this.pointerIds[i] = other.pointerIds[i];
      }
      this.xMid = other.xMid;
      this.yMid = other.yMid;
      this.pressureMid = other.pressureMid;
      this.dx = other.dx;
      this.dy = other.dy;
      this.diameter = other.diameter;
      this.diameterSq = other.diameterSq;
      this.angle = other.angle;
      this.isDown = other.isDown;
      this.action = other.action;
      this.isMultiTouch = other.isMultiTouch;
      this.diameterIsCalculated = other.diameterIsCalculated;
      this.diameterSqIsCalculated = other.diameterSqIsCalculated;
      this.angleIsCalculated = other.angleIsCalculated;
      this.eventTime = other.eventTime;
    }

    // -------------------------------------------------------------------------------------------------------------------------------------------

    /**
     * True if number of touch points >= 2.
     */
    public boolean isMultiTouch() {
      return isMultiTouch;
    }

    /**
     * Difference between x coords of touchpoint 0 and 1.
     */
    public float getMultiTouchWidth() {
      return isMultiTouch ? dx : 0.0f;
    }

    /**
     * Difference between y coords of touchpoint 0 and 1.
     */
    public float getMultiTouchHeight() {
      return isMultiTouch ? dy : 0.0f;
    }

    /**
     * Fast integer sqrt, by Jim Ulery. Much faster than Math.sqrt() for integers.
     */
    private int julery_isqrt(int val) {
      int temp, g = 0, b = 0x8000, bshft = 15;
      do {
        if (val >= (temp = (((g << 1) + b) << bshft--))) {
          g += b;
          val -= temp;
        }
      } while ((b >>= 1) > 0);
      return g;
    }

    /**
     * Calculate the squared diameter of the multitouch event, and cache it. Use this if you don't need to perform the sqrt.
     */
    public float getMultiTouchDiameterSq() {
      if (!diameterSqIsCalculated) {
        diameterSq = (isMultiTouch ? dx * dx + dy * dy : 0.0f);
        diameterSqIsCalculated = true;
      }
      return diameterSq;
    }

    /**
     * Calculate the diameter of the multitouch event, and cache it. Uses fast int sqrt but gives accuracy to 1/16px.
     */
    public float getMultiTouchDiameter() {
      if (!diameterIsCalculated) {
        if (!isMultiTouch) {
          diameter = 0.0f;
        } else {
          // Get 1/16 pixel's worth of subpixel accuracy, works on screens up to 2048x2048
          // before we get overflow (at which point you can reduce or eliminate subpix
          // accuracy, or use longs in julery_isqrt())
          float diamSq = getMultiTouchDiameterSq();
          diameter = (diamSq == 0.0f ? 0.0f : (float) julery_isqrt((int) (256 * diamSq)) / 16.0f);
          // Make sure diameter is never less than dx or dy, for trig purposes
          if (diameter < dx) {
            diameter = dx;
          }
          if (diameter < dy) {
            diameter = dy;
          }
        }
        diameterIsCalculated = true;
      }
      return diameter;
    }

    /**
     * Calculate the angle of a multitouch event, and cache it. Actually gives the smaller of the two angles between the x axis and the line
     * between the two touchpoints, so range is [0,Math.PI/2]. Uses Math.atan2().
     */
    public float getMultiTouchAngle() {
      if (!angleIsCalculated) {
        if (!isMultiTouch) {
          angle = 0.0f;
        } else {
          angle = (float) Math.atan2(ys[1] - ys[0], xs[1] - xs[0]);
        }
        angleIsCalculated = true;
      }
      return angle;
    }

    // -------------------------------------------------------------------------------------------------------------------------------------------

    /**
     * Return the total number of touch points
     */
    public int getNumTouchPoints() {
      return numPoints;
    }

    /**
     * Return the X coord of the first touch point if there's only one, or the midpoint between first and second touch points if two or more.
     */
    public float getX() {
      return xMid;
    }

    /**
     * Return the array of X coords -- only the first getNumTouchPoints() of these is defined.
     */
    public float[] getXs() {
      return xs;
    }

    /**
     * Return the X coord of the first touch point if there's only one, or the midpoint between first and second touch points if two or more.
     */
    public float getY() {
      return yMid;
    }

    /**
     * Return the array of Y coords -- only the first getNumTouchPoints() of these is defined.
     */
    public float[] getYs() {
      return ys;
    }

    /**
     * Return the array of pointer ids -- only the first getNumTouchPoints() of these is defined. These don't have to be all the numbers from 0 to
     * getNumTouchPoints()-1 inclusive, numbers can be skipped if a finger is lifted and the touch sensor is capable of detecting that that
     * particular touch point is no longer down. Note that a lot of sensors do not have this capability: when finger 1 is lifted up finger 2
     * becomes the new finger 1.  However in theory these IDs can correct for that.  Convert back to indices using MotionEvent.findPointerIndex().
     */
    public int[] getPointerIds() {
      return pointerIds;
    }

    /**
     * Return the pressure the first touch point if there's only one, or the average pressure of first and second touch points if two or more.
     */
    public float getPressure() {
      return pressureMid;
    }

    /**
     * Return the array of pressures -- only the first getNumTouchPoints() of these is defined.
     */
    public float[] getPressures() {
      return pressures;
    }

    // -------------------------------------------------------------------------------------------------------------------------------------------
    public boolean isDown() {
      return isDown;
    }

    public int getAction() {
      return action;
    }

    public long getEventTime() {
      return eventTime;
    }
  }

  // ------------------------------------------------------------------------------------

  /**
   * A class that is used to store scroll offsets and scale information for objects that are managed by the multitouch controller
   */
  public static class PositionAndScale {

    private float xOff, yOff, scale, scaleX, scaleY, angle;
    private boolean updateScale, updateScaleXY, updateAngle;

    /**
     * Set position and optionally scale, anisotropic scale, and/or angle. Where if the corresponding "update" flag is set to false, the field's
     * value will not be changed during a pinch operation. If the value is not being updated *and* the value is not used by the client
     * application, then the value can just be zero. However if the value is not being updated but the value *is* being used by the client
     * application, the value should still be specified and the update flag should be false (e.g. angle of the object being dragged should still
     * be specified even if the program is in "resize" mode rather than "rotate" mode).
     */
    public void set(float xOff, float yOff, boolean updateScale, float scale, boolean updateScaleXY, float scaleX, float scaleY,
                    boolean updateAngle, float angle) {
      this.xOff = xOff;
      this.yOff = yOff;
      this.updateScale = updateScale;
      this.scale = scale == 0.0f ? 1.0f : scale;
      this.updateScaleXY = updateScaleXY;
      this.scaleX = scaleX == 0.0f ? 1.0f : scaleX;
      this.scaleY = scaleY == 0.0f ? 1.0f : scaleY;
      this.updateAngle = updateAngle;
      this.angle = angle;
    }

    /**
     * Set position and optionally scale, anisotropic scale, and/or angle, without changing the "update" flags.
     */
    protected void set(float xOff, float yOff, float scale, float scaleX, float scaleY, float angle) {
      this.xOff = xOff;
      this.yOff = yOff;
      this.scale = scale == 0.0f ? 1.0f : scale;
      this.scaleX = scaleX == 0.0f ? 1.0f : scaleX;
      this.scaleY = scaleY == 0.0f ? 1.0f : scaleY;
      this.angle = angle;
    }

    public float getXOff() {
      return xOff;
    }

    public float getYOff() {
      return yOff;
    }

    public float getScale() {
      return !updateScale ? 1.0f : scale;
    }

    /**
     * Included in case you want to support anisotropic scaling
     */
    public float getScaleX() {
      return !updateScaleXY ? 1.0f : scaleX;
    }

    /**
     * Included in case you want to support anisotropic scaling
     */
    public float getScaleY() {
      return !updateScaleXY ? 1.0f : scaleY;
    }

    public float getAngle() {
      return !updateAngle ? 0.0f : angle;
    }
  }

  // ------------------------------------------------------------------------------------
  public static interface MultiTouchObjectCanvas<T> {

    /**
     * See if there is a draggable object at the current point. Returns the object at the point, or null if nothing to drag. To start a multitouch
     * drag/stretch operation, this routine must return some non-null reference to an object. This object is passed into the other methods in this
     * interface when they are called.
     *
     * @param touchPoint The point being tested (in object coordinates). Return the topmost object under this point, or if dragging/stretching the whole
     *                   canvas, just return a reference to the canvas.
     * @return a reference to the object under the point being tested, or null to cancel the drag operation. If dragging/stretching the whole
     * canvas (e.g. in a photo viewer), always return non-null, otherwise the stretch operation won't work.
     */
    public T getDraggableObjectAtPoint(PointInfo touchPoint);

    /**
     * Get the screen coords of the dragged object's origin, and scale multiplier to convert screen coords to obj coords. The job of this routine
     * is to call the .set() method on the passed PositionAndScale object to record the initial position and scale of the object (in object
     * coordinates) before any dragging/stretching takes place.
     *
     * @param obj               The object being dragged/stretched.
     * @param objPosAndScaleOut Output parameter: You need to call objPosAndScaleOut.set() to record the current position and scale of obj.
     */
    public void getPositionAndScale(T obj, PositionAndScale objPosAndScaleOut);

    /**
     * Callback to update the position and scale (in object coords) of the currently-dragged object.
     *
     * @param obj               The object being dragged/stretched.
     * @param newObjPosAndScale The new position and scale of the object, in object coordinates. Use this to move/resize the object before returning.
     * @param touchPoint        Info about the current touch point, including multitouch information and utilities to calculate and cache multitouch pinch
     *                          diameter etc. (Note: touchPoint is volatile, if you want to keep any fields of touchPoint, you must copy them before the method
     *                          body exits.)
     * @return true if setting the position and scale of the object was successful, or false if the position or scale parameters are out of range
     * for this object.
     */
    public boolean setPositionAndScale(T obj, PositionAndScale newObjPosAndScale, PointInfo touchPoint);

    /**
     * Select an object at the given point. Can be used to bring the object to top etc. Only called when first touchpoint goes down, not when
     * multitouch is initiated. Also called with null on touch-up.
     *
     * @param obj        The object being selected by single-touch, or null on touch-up.
     * @param touchPoint The current touch point.
     */
    public void selectObject(T obj, PointInfo touchPoint);
  }
}
